1. Field of Invention
The present invention relates to a polycyclohexylenedimethylene terephthalate resin composition, and more specifically to an economical, high color-resistant, flame-retardant polycyclohexylenedimethylene terephthalate resin composition containing a non-halogen flame retardant aid, bis(2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-oxo-4-hydroxymethyl)phenylphosphonate.
2. Description of the Related Art
As needs for high heat-resistant materials are recently increasing, necessity is heightened for engineering plastic with heat resistance of continuous duty temperature of 250° C. or higher while satisfying moldability suitable for producing electronic materials and automobile parts with complex shapes. Especially, thermoplastic resins having high heat resistance are needed as the core component materials of the high-tech industry of the next generation, such as displays, solar cells, flexible plastic materials for electronic paper, materials for space industry, other electronics/semiconductors, etc. To be used in displays and flexible plastic materials for solar cells, polymer materials having high heat resistance with the glass transition temperature of 330° C. or higher, as well as high transparency, low hygroscopic property, and low shrinkage property are needed. However, such novel materials still have not been developed yet.
To ensure heat resistance of a polymer, a molecular structure which is very stable against heat should be constituted by introducing an aromatic group. However, the development is hindered by low transparency due to interactions between aromatic polymer chains, optical anisotropy, an innately high coefficient of expansion of an organic polymer, etc.
Recently, super engineering plastics which may replace poly(ether ether ketone) (PPEK), which has satisfying heat resistance but bad moldability, are being developed. Representative polymers include: i) polyamide-based PA46 (Stanyl, DSM), polyphthalamide (PPA) (or PA6T or Nylon6T; representative products include Zytel HTN®, Amodel®, and) Grivory®), and PA9T (or Nylon9T®; Genestar); ii) a wholly aromatic polyester-based display polymer (liquid crystalline polymer (LCP); representative products include Xydar® and Sumikasuper®); and iii) polyester-based polycyclohexylenedimethylene terephthalate (PCT; representative products includes Thermx® of DuPont) induced from alicyclic monomers.
PCT, amongst all, has a crystallization rate slower than that of polybutylene terephthalate (PBT) but faster than that of polyethylene terephthalate (PET), exhibits high heat resistance, and enables an injection molding. Further, due to the relatively high cost competitiveness, PCT has high potential applicability. Furthermore, PCT is a polymer having the highest melting point amongst existing polyester-based polymers except liquid crystal polymers, and exhibits low water absorption and excellent color resistance against heat compared to other polyamide-based polymers.
Generally, thermoplastic resins such as polycyclohexylenedimethylene terephthalate (PCT) resins, etc., are applied in numerous products due to their excellent processability and mechanical features. However, since thermoplastic resins are not innately resistant to fire, it has been regulated by law to only use polymer resins which satisfy flame resistance standards throughout the world. Therefore, flame retardants are compounded in resins to provide flame retardancy in thermoplastic resins. Examples of the conventional flame retardants are halogen-based flame retardants, polyphosphoric acid-based flame retardants (inorganic phosphorus-based flame retardants) such as red phosphorus, ammonium polyphosphate, etc., organic phosphorus-based flame retardants represented by triaryl phosphorus ester compounds, and metal hydroxides. Representative examples of flame retardant aids used in combination with the flame retardants are antimony oxides, melanin compounds, etc.
Typically, flame retardancy is incorporated in thermoplastic resins by compounding halogen-based flame retardants with antimony oxide (Sb2O3) as a flame retardant aid. However, although the halogen-based flame retardants (organic halogen-based flame retardants and halogen-containing organic phosphorus flame retardants) are widely used due to their excellent flame-retardancy the halogen-based compounds can be volatilized and produce halogenated hydrogen gas during processing, thereby causing metal corrosions. Also, gas produced during combustion is problematic as it is harmful to human body. According to the regulation of harmful substances such as RoHS and PoHS along with the materials described above, various regulations are imposed to limit the usage of products containing halogen-based compounds as electrical and electronic components. Therefore, there is a rapidly increasing need for resins containing non-halogen-based flame retardants.
A flame retardation technology for polymer resins including inorganic compounds such as magnesium hydroxide, aluminum hydroxide, etc., as flame retardants using non-halogen-based compounds is suggested. JP Patent Application Publication No. 1998-204276 suggests a method of adding a flame retardant to resins by mixing aluminum hydroxide (ATH), at least one nitrogen compound and red phosphorus, and adding to unsaturated polyester resins. However, the necessity of use of aluminum hydroxide in large quantity results in deterioration of mechanical properties of a resin composition. Further, KR Patent Application Publication No. 2007-0064924, describes a flame retardation technology of acrylonitrile-butadiene-styrene copolymer resins (ABS resins), but it is not environment-friendly since the used flame retardant a bromine-based organic compound.
Meanwhile, flame retardants are considered as comparably expensive compounds, and thus to produce more economical resin compounds, numerous research has been conducted to develop flame retardant aids which could maintain or enhance flame retardancy while reducing the content of flame retardants. However, it is not easy to determine the optimal flame retardant aid and the appropriate content thereof.